(1) Field of the Invention
The present invention relates to a die for extruding a honeycomb structural body (hereinafter referred to as "honeycomb forming die") and a method of manufacturing the same, and more particularly, the invention relates to a honeycomb forming die used to extrude a plasticized material to form a honeycomb structural body in which a plate made of a wear resistant alloy (for instance, hard metal) is joined to the die front face portion to which forming slits are to be formed, and the forming slits are formed in the wear resistant alloy plate. The invention also relates to a method of manufacturing the same.
(2) Description of the Prior Art
Heretofore, there has been known a honeycomb forming die as shown in FIG. 1 (FIG. 1a is a plane view of the honeycomb forming die, and FIG. 1b is a sectional side view of the forming die shown in FIG. 1a as viewed from an arrow A-A'). More particularly, the honeycomb forming die shown in FIG. 1 is a so-called integral structure in which honeycomb forming slits 3 (hereinafter referred to as forming slits) having a specified depth are formed from the die front face 1 toward the die rear face 2 in such a sectional profile as to conform to the sectional profile of a honeycomb structural body to be shaped (a rectangular section honeycomb in the forming die shown in FIG. 1), and a plurality of openings 4 are independently formed from the die rear face 2 toward the die front face 1 to communicate with the above forming slits 3.
The honeycomb forming die shown in FIG. 1 is generally produced as follows:
That is, a block body is prepared from a metallic material by means of a general purpose machine tool such as lathe or the like, and numerous independent openings 4 are bored from one of the faces (die rear face 2) of the block body toward the other face (die front face 1) of the block body by means of a drilling machine. Thereafter, the honeycomb forming slits 3 are worked from the die front face 1 toward the die rear face 2 of the block body, for instance, by electrical discharge machining or the like to communicate with the openings 4.
When the honeycomb structural body is shaped by using the honeycomb forming die thus produced, a raw material of the honeycomb structural body to be shaped, such as a plasticized material of ceramic, is press fed into all the openings 4 and the plasticized material thus press fed flows into the forming slits while being squeezed, whereby the ceramic honeycomb structural body is continuously extruded from the forming slits 3.
However, when the honeycomb structural body is extruded by using such a conventional honeycomb forming die, the forming slits 3 are worn by the plasticized material passing through the forming slits 3, so that the width of the slits becomes larger. Consequently, in order to assure the dimensional precision of the honeycomb structural bodies, there is a problem that exchange of expensive dies must be made at a number of times. Particularly, when the honeycomb structural bodies are shaped by using a raw material of alumina or silicon carbide, a raw material of mullite having a coarse particle size or the like, the wear of the forming slits 3 is conspicuous, so that the durable life of the die becomes remarkably shorter.
Further, according to the conventional honeycomb forming die, the dimensional variations in the forming slits causes the difference in the extruding rate of the material to be extruded over the forming slits, so that there are problems that cracks are formed in the honeycomb structural body extruded thereby in a firing process, or the material is not extruded into a honeycomb shape.